1. Field of the Invention
The present invention relates generally to a durable, multiple-use needle-less (or needle-free) jet injection device and methods of its making, operation, and use. Particularly, this invention relates to a durable gas-powered, rechargeable, hypodermic jet injection device which comprises a hand-held injector having a refillable drug cartridge carrying injectable medication, a sealed cylinder of pressurized gas, a mechanism for penetrating the gas cylinder preparatory to effecting an injection, and a trigger device for releasing gas from the gas cylinder in order to effect an injection by action of the pressurized gas on an injection piston
2. Related Technology
Needle-less or needle-free hypodermic jet injection devices have been in commercial use for over 40 years. A number of these devices have used pressurized gas to power a hypodermic jet injection. The related technology includes a number of teachings for gas-powered injection devices, including: U.S. Pat. No. 4,596,556, issued Jun. 24, 1986 to J. Thomas Morrow, et al.; U.S. Pat. No. 4,913,699; issued Apr. 3, 1990 to James S. Parsons; and U.S. Pat. No. 5,730,723, issued Mar. 24, 1998, to Thomas P. Castellano, et al. WIPO publication WO 97/37705 also discloses a gas powered disposable needle-less hypodermic jet injector.
The Morrow, et. al. ""556 patent is believed to teach a reusable hypodermic jet injection device in which a housing receives a shell or cartridge having a bore leading to a discharge aperture. Within the bore is received both a plunger sealingly engaging the bore, and a pressurized gas cylinder which rests against the plunger. The injection device includes a ram which has a penetrating tip confronting a penetrable wall section and seal of the gas cylinder, and a discharge mechanism for driving the ram through the penetrable wall section of the gas cylinder when a trigger device is released. Discharge of the pressurized gas from the cylinder drives the plunger to effect a jet injection, and also drives the seal of the gas cylinder to effect resetting of the discharge mechanism. The shell with its plunger, and spent gas cylinder, is discarded after an injection; and a new shell pre-filled with medication and with a new gas cylinder is used for each injection.
The Parsons ""699 patent is believed to teach a single-use jet injector which is totally discarded after one use. This injector is believed to have a body with a pair of gas chambers separated by a breakable valve. One of the gas chambers contains a pressurized gas, while the other chamber is sealingly bounded by a piston which drives a plunger. The plunger sealingly bounds a chamber into which a dose of medication is loaded by the user before the injection. This medication dose chamber leads to an injection orifice so that when the valve is broken, the piston and plunger are moved by pressurized gas communicated to the second chamber, and the plunger drives the medication forcefully out of the injection orifice to form an injection jet. After a single use, the device is discarded.
The Castellano ""723 patent, which was issued in 1998 and which does not cite the earlier Parsons ""699 patent, is believed to teach substantially the same subject matter as Parsons et al.
WIPO publication WO 97/37705 published pursuant to a Patent Cooperation Treaty (PCT) application for joint inventors Terence Weston and Pixey Thomlea, is believed to disclose a disposable hypodermic jet injector in which the device is powered by a gas pressure spring of the type common in the tool and die art as a substitute for the conventional metal spring-powered ejector pin. In the Weston device, the ram of the gas pressure spring is held in a contracted position by a trigger mechanism. When the trigger mechanism is released, the gas pressure spring is supposed to expand and drive a piston sealingly received in a bore and leading to a fine-dimension orifice in order to produce a jet hypodermic injection from liquid held in the bore ahead of the piston.
The Weston device is thought to have several deficiencies: such as difficult and costly manufacturing and sterilization processes, because pressurized gas and a drug dose need to be contained in the same package; and including a possible inability to endure long-term storage while still retaining the gas pressure in the gas spring to power an injection, and also maintaining the medication integrity. In other words, the gas pressure spring of the Weston device contains only a small quantity of gas, and depends upon the sealing relationship of the ram of this spring with a cylinder within which the ram is movably and sealingly received in order to retain this gas pressure. Even a small amount of gas leakage over time will be enough to render this injector inoperative.
In view of the above, it is desirable and is an object for this invention to provide a needle-less jet injection device which reduces the severity of or avoids one or more of the limitations of the conventional technology.
Thus, it is an object of this invention to provide a durable, needle-free gas-powered jet injector utilizing a pressurized gas source which is hermetically sealed until it is opened in preparation for effecting the jet injection.
This jet injector includes a unique valving mechanism in one operative position containing the pressurized gas communicating from the opened gas source, until the valving mechanism is moved to a second operative position communicating the pressurized gas to an injection piston.
Further, an object of this invention is to provide such a jet injector in which the device is particularly efficient and elegant with respect to the design, functionality, and materials utilization of the components of the device. In other words, the parts count of the device is small, and materials are utilized which ease and reduce the cost of manufacture of the device. Nevertheless, because of the unique design of the device, inexpensive materials of relatively low strength are able to serve well. For example, the valving device may be made of injection molded plastic, and yet contain pressures of over 1000 PSI in preparation for a jet injection.
Accordingly, an embodiment of the present invention provides a jet injection device comprising: a device body having a forward end; an injection cylinder carried at the forward end of said device body and having a cylinder bore in which an injection piston is movable to cooperatively define a variable-volume chamber for holding a dose of liquid medication; a fine-dimension injection orifice in liquid flow communication with said variable-volume chamber to receive liquid medication and discharge this medication as a high velocity forceful jet for jet injection of medication upon forceful movement of said injection piston in said cylinder; a power source in said device body for forcefully moving said piston in said cylinder in response to communication of gas pressure to a gas pressure piston, a source of gas pressure; and a trigger assembly for effecting communication of pressurized gas from said source to said gas pressure piston, said trigger assembly including a stem member with a pair of ports spaced axially apart, and a pair of axially spaced apart seal members movable along said stem from a first position in which said seal members bracket only a single one of said axially spaced apart ports, said trigger assembly being manually movable axially to a second position in which said pair of seal members bracket both of said pair of axially spaced ports to communicate pressurized gas from one of said pair of ports to the other of said pair of ports and to said gas pressure piston.
According to a further aspect this invention provides: a method of providing a jet injection device, said method comprising steps of: providing a device body having a forward end; providing an injection cylinder, and carrying said injection cylinder at a forward end of said device body, providing said injection cylinder with a cylinder bore in which an injection piston is movable to cooperatively define a variable-volume chamber for holding a dose of liquid medication; providing a fine-dimension injection orifice in liquid flow communication with said variable-volume chamber to receive liquid medication, and discharging the liquid medication as a high velocity forceful jet for jet injection of medication upon forceful movement of said injection piston in said cylinder; providing a power source in said device body for forcefully moving said injection piston in said cylinder in response to communication of gas pressure to a gas pressure piston, providing a source of gas pressure; and providing a trigger assembly for effecting communication of pressurized gas from said source to said gas pressure piston, configuring said trigger assembly to include a stem member with a pair of ports spaced axially apart, and providing a pair of axially spaced apart seal members movable along said stem from a first position in which said seal members bracket only a single one of said axially spaced apart ports, providing for said trigger assembly to be manually movable axially to a second position in which said pair of seal members bracket both of said pair of axially spaced ports to communicate pressurized gas from one of said pair of ports to the other of said pair of ports and to said gas pressure piston.
Additional objects and advantages of this invention will appear from a reading of the following detailed description of two exemplary preferred embodiments of the invention, taken in conjunction with the appended drawing Figures, in which the same reference numeral is used throughout the several views to indicate the same feature, or features which are analogous in structure or function.